This invention relates to a vertical treating apparatus for use in various treatments, such as the heat treatment of objects to be treated, e.g., semiconductor wafers.
Conventionally vertical heat treating apparatuses have been generally used in oxidation, diffusion, CVD, etc. of objects to be treated, such as semiconductor wafers (hereinafter called wafers) in fabrication processes of semiconductors. Such a vertical heat treating apparatus includes a process tube as a heat treating unit which holds wafers therein to conduct a heat treatment, and a load lock chamber below the process tube and a manifold therebetween. The manifold is a space unit interconnecting the process tube and the load lock chamber and also defines a shielding space for shielding the wafers which are to be treated or have been treated in the process tube.
As shown in FIG. 6, wafers W are set on a wafer boat 12 from the side of the load lick chamber 6 and are loaded into the process tube 1. In the load lock chamber 6 there is provided a boat elevator 13 as a lift mechanism for moving up and down the wafer boat 12 to load the wafers W into the process tube 1 through an opening 3 of the manifold 5. On the upper surface of the boat elevator 13 there is provided a cap 16 which is a closing member for closing the opening 3 of the manifold 5 when the wafer boat 12 is loaded and for shutting the process tube 1 and the load lock chamber 6 from each other. An 0-ring 18 is attached to the peripheral edge of the upper surface of the cap 16 for sealing between the opening surface 15 of the manifold 5 and the cap 16. The cap 16 is flexibly supported by a plurality of coil springs 17 on the upper surface of the arm of the boat elevator 13 so as to be brought into close contact with the opening surface 15 of the manifold 5 which is a stationary member.
But in the vertical heat treating apparatus of such structure, when the wafer boat 12 is lowered to transfer wafers W, in the case that coil spring 17 supporting the wafer boat 12 is soft, the coil spring 17 is flexed due to a load of, e.g., the wafer boat 12, etc. mounted on the cap 16 and tilts the wafer boat 12. As a result, the arm of the wafer transfer means can come in contact with the wafer boat 12 or wafers W mounted on the arm, and particles can stick to the wafers W. Accordingly there is a problem that yields may be lowered. Another problem is that the arm, etc. of the wafer transfer means collide with the wafer boat 12, and the wafers W are damaged. To solve these problems, consideration has been given to the use of a coil spring 17 which is hard. But a problem with this case is that the cap 16 is not brought into perfect close contact with the opening surface 15 of the manifold 5.
To solve these problems, as shown in FIG. 7, reliance has been placed on the cap 16 which comprises a disk 16a secured to the upper surface of the arm of the boat elevator 13, and an O-ring support member 16c connected to the disk 16a through a bellows 16b and having an O-ring 18 which is brought into close contact with the opening surface 15 of the manifold 5 (Japanese Utility Model Laid-Open Publication No. 120326/1988). But problems with such cap 16 include a complicated structure that accordingly incurs high costs, and the inside surface of the bellows 16b has a number of concavities and convexities which cannot be easily cleaned.